Electrical cut-out



July 17, 1928. 1,677,692

J. F- STOKES ELECTRICAL CUT-OUT Filed July 9, 1927 INVENTOR. a 2441, Jam

A ATTORNEY Patented July 17, 1928.

UNITED STATES renew. PATENT orica.

JOHN FRASER STOKES, OF NEW YORK, N. Y., ASSIGNOR T RAINBOW LIGHT, INC., A

CORPORATION OF NEW YORK ELECTRICAL CUT-OUT.

Application filed July 9,

My invention relates to certain new and useful improvements in electrical cut-outs designed particularly for use in connection with the operation of luminous discharge I tubes employing a rarefied gaseous atmosphere through which an electric current is passed to secure illumination. The invention may be used in connection with any electric appliance in which similar or ana1 ogous conditions are encountered as With these luminous discharge tubes.

In the operation of a luminous discharge tube a very high starting voltage is required. When the tube has been once start ed the voltage necessary to maintain it in operation is very much reduced and-may be or less of the starting voltage. These luminous discharge tubes are usually operated by means of transformers, the prima- 30 ries of which are connected to the usual 110' volt or 220 volt alternating current supply, and the transformers are designed usually to have an open circuit voltage .suificiently high to start the tube. Obviously, should the tube break or should the secondary circuit be broken or grounded, the open circuit voltage will rise to its maximum value. Under such condition the transformer will constitute a menace to life as well as a source of l fire. Such a condition would not be corrected by the use of an ordinary fusible cutout in the primary circuit, for the reason that in the operation of these luminous tubes limited current transformers are employed 3'5 with high inductive reactance, or auxiliary inductance coils are used in order to limit the current to a desired commercial value. Therefore, should the secondary be open circuited for any reason, the primary current would be of its minimum value. Thus, the" use of a fusible cut-out in the primary circuit is ineffective to meet the condition above pointed out.

With my improved cut-out I provide for the breaking of the primary circuit, should the voltage in the secondaryrise to a dangerous value, as, for example, when the transformer is used for the operation of a luminous discharge tube and the tube 80 breaks or if the secondary circuit is broken or becomes grounded.

In order that the invention may be better understood, attention is directed to the ac companying drawing, showing an embodiment thereof, the mechanical parts being 1927. Serial No. 204,481.

illustrated in pers ective. and the circuits anld transformer being shown diagrammatica y.

I here illustrate the invention applied in connection with a, luminous discharge tube,

although, as I have pointed out, it may be utilized in connection with any electrical appliance or apparatus in which the same or analogous characteristics are present. 1 represents a luminous discharge tube filled with a rarefied gaseous atmosphere such as neon or argon having terior electrodes 2-2 of the usual type. The representation of the tube is purely diagrammatic. Ordinarily, these tubes are very long and are 7 bent into the form of letters or symbols to constitute a sign. The transformer 3 has the secondary terminals 4 and 5 in circuit, as shown, with the electrodes 22. It also has the primary terminals 6-6 in a primary circuit 7 connected to the usual alternating current supply.

The transformer 3 is so designed as to have an open circuit voltage at the secondary sufficiently high to start the tube,-and it is also designed, or is provided with associated apparatus, to limit the current of the secondary circuit. With an ordinary neon sign this secondary current is of the order of 30 milliamperes more or less.

In the primary circuit. 7 is a switch 8, which may be of any suitable construction. The switch shown is provided with a tumbler 9 which when moved to the right will break the primary circuit. This tumbler is shown as being operated by a bail 10 having a spring 11 tending to move the same when released to break the primary circuit. stud 12 on the bail 10 cooperates with a notch in a trigger 13 so as to normally hold the switch in its closed position. This trigger is normally held in the position shown by a link 14; made of suitable fusible wire.

The said link preferably extends in frontof the two secondary terminals 4 and 5, as shown, so as to form two gaps between said terminals and the link. The distance between link 14- and the two terminals 4 and 5 is such that under open circuit conditions the secondary voltage will be sufficient to bridge the two gaps in series, but under normal working conditions the voltage will not be sufiicient for this purpose. If the tube 1 is then operating under proper condition with the elements of the cut-out in the position shown, when the primary circuit is closed, there will be an instantaneous rise of voltage to the maximum Value in starting the tube mum value.

and momentary sparking will take place between the secondary terminals 4 and 5 and the link 14. This is only momentary, however, and will not be sufficient to fuse the link. As soon as the tube starts, the voltage will drop and the sparking will cease. If, however, the tube should break or the secondary circuit should be broken, the secondary voltage will riseto its maximum value, thus short circuiting the terminals 4 and 5 through the link 14, and in a few seconds the link will fuse, permitting the trigger. 13 to drop, whereupon bail 10 will operate the tumbler 9 to break the primary circuit. Should the secondary circuit at any time become accidently grounded the cut-out switch will also automatically operate, since that switch is also grounded (not shown) and the effect will then be to bring the terminals 4 and 5 in multiple with respect to the link 14 insteadof being in series with each other, as is normally the case. In other words, the effect of grounding the secondary is practically to reduce the spark gap and thus permit the link to be fused even though the secondary potential may not rise to its maxi- In order that the automatic operation of the switch, when either secondary is grounded, may be more clearly understood, the following explanation is made, the secondary lead from terminal 4 being re ferredto as the upper secondary lead and the secondary lead from terminal 5 being referred to as the lower secondary lead. I

In a typical case when the apparatus is operating under normal conditions, the voltage across the secondary terminals will he say from one-half to one-third the open circult voltage, and as explained above, the gapsbetween the link 14 and the secondary terminals are so adjusted that at the reduced operatmg voltage there will be no sparking between these terminals and the link. Under normal conditions, in other words, the gaps are in series. Let it now be supposed that the upper secondary lead from terminal 4 ecomes grounded, ing the insulation covering both leads. In this case it will be apparent that the secondary termlnal will be at the same potential as the link, namely, zero otential, since the link 14 is always groun ed. Consequentlythe operating voltage drop across the secondary terminals will now be applied to the single gap between the terminal 5 and-link 14, sparking will occur and the link will fuse. In the same way should the lower secondary lead become grounded, sparking w ll take place between the secondary terminal 4 and the link, resulting in sparking and fusion of the link.

Although I prefer to arrange the link 14 for instance by punctur adjacent both of the secondary terminals, as explained, this is not strictly necessary. The gap may exist between only one of these terminals and the link 14, in which case the secondary circuit will be grounded with respect to the link. With the proposed modification the single spark gap between one of the secondary terminals and the link will be so proportioned as to permit passage of the current under open circuit voltage conditions but prevent passage of current under normal working conditions. Therefore, should the tube break or should the secondary circuit be broken so as to result 'in the maximum open circuit volt-age in the 1. An electric cut-out designed for use inconnection with transformers and to prevent the continuation of open circuit secondary voltage conditions, comprising in combination, a transformer, a primary circuit, a cutout switch in the primary circuit normally closed, and means whereby said switch will operate to break the primary circuit under the effect of continued open circuit voltage conditions in the secondary, substantially as set forth.

2. In an electric cut-out, the combination of a transformer operating under a normal voltage but intended to momentarily develo a voltage of abnormally high value, a pnmary circuit connected to the transformer, a normally closed cut-out switch in the primary circuit, .and means whereby .said outout switch will operate to open the primary circuit ifan abnormally high voltage condition continues in the secondary circuit, said means being non-res onsive to a momentary volt-age rise, su stantially as set forth.

3. In an electric cut-out, the combination of .a transformer intended to operate at a normal voltage but momentarily developing a voltage of abnormally high value, a primary circuit, a normally closed switch in the primary circuit, and a fusible link co-operating with thesecondary in the transformer so that a continued condition of abnormally high voltage will fuse said link and permit the cut-out switch to open the primary circuit, substantially as set forth.

4. In an electric cut-out, the combination of a transformer, secondary terminals therefor, a primary circuit, a switch in the primary circuit, said switch being normally closed, and a fusible link normally holding the switch closed and having a spaced relationship, substantially as set forth, with respect to a secondary terminal of the transformer.

5. In an electric cut-out, the combination of a transformer, secondary terminals therefor, a primary circuit, a switch in the primary circuit, said switch bein normally closed, and a fusible link norma 1y holding the switch closed and having a spaced relationship, substantially as set forth, with respect to both secondary terminals of the transformer.

6. In an electric cut-out, the combination with a transformer, secondary terminals therefor, a luminous tube in circuit with the secondary terminals, a primary circuit, a normally closed switch in the primary circuit, and a fusible link normally holding said switch closed and having a spaced relationship, substantially as set forth, with respect to said secondary terminals.

7. In an electric cut-out, the combination of a luminous tube, a transformer, secondary terminals for said transformer in circuit with the tube, a primary circuit, an electric switch in the primary circuit, said switch being normally closed, a trigger holding said switch normally closed, and a fusible link connected to said trigger and having 'a spaced relationship, substantially as set forth with respect to said secondary terminals.

JOHN FRASER STOKES. 

